RFID tags are known in the art. These so-called tags often assume the form factor of a label or a literal “tag” but are also sometimes integrated with a host article and/or its packaging. RFID tags typically comprise an integrated circuit and one or more antennas. The integrated circuit typically carries out a variety of functions including modulating and demodulating radio frequency signals, data storage, and data processing. Some integrated circuits are active or self-powered (in whole or in part) while others are passive, being completely dependent upon an external power source (such as an RFID tag reader) to support their occasional functionality.
There are proposals to utilize RFID tags to individually identify individual items. The Electronic Product Code (EPC) as managed by EPCGlobal, Inc. represents one such effort in these regards. EPC-based RFID tags each have an utterly-unique serial number (within the EPC system) to thereby uniquely identify each tag and, by association, each item associated on a one-for-one basis with such tags. (The corresponding document entitled EPC Radio-Frequency Identity Protocols Class-1 Generation-2 UHF RFID Protocol for Communications at 860 MHz-960 MHz Version 1.0.9 (often referred to as “EPC GEN2”) is hereby fully incorporated herein by this reference.)
Being able to read and then uniquely identify each item within a manufacturing facility, a cargo container, a staging area, or in a retail display area offers any number of useful opportunities. Unfortunately, the very nature of RFID-based technology, coupled with a correspondingly potentially enormous number of individually-tagged items, also gives rise to a number of challenges as well. As one simple example in these regards, an end user employing a handheld RFID tag reader may often be uncertain when they are, in fact, “done” with reading a given plurality of RFID tags.
An associate on the floor of a large retail-sales facility, for example, will not typically know just how many RFID tags are, in fact, to be read during a particular reading exercise. This problem exists, at least in part, because there is nothing inherent or intrinsic about the EPC GEN2 coding scheme (or its functional counterparts) and/or its corresponding reading protocol that identifies when all RFID tags that are to be read have been read.
The aforementioned problem is further acerbated by at least some RFID-tag protocols that permit an RFID tag to have any of a plurality of read states. The aforementioned EPC GEN2 approach, for example, provides for a so-called A inventory state and a B inventory state. This permits, for example, a group of RFID tags to be inventoried without necessarily requiring each and every RFID tag to respond to the reader. A reader can be configured, for example, to request that RFID tags having an A inventory state respond to a read request while permitting RFID tags having a B inventory state to essentially ignore the read request. Generally speaking, the “A” state comprises a default state and hence represents the tag's state when initially powering up. Once a tag has been read its read state changes from “A” to “B.”
The EPC GEN2 standard specifies four different sessions that provide for differences with respect to how a read tag persists a “B” state. In Session “0” a read tag will persist this “B” state until power is lost and then the tag reverts immediately to the “A” state. In Session “1” a read tag will persist its “B” state for a period of time ranging from 500 ms to 5 seconds and will then automatically revert to the “A” state. In Session “2” and “3” a read tag will remain in the “B” state until power is lost. Then, once power is lost, the read tag will persist its “B” state for at least an additional 2 seconds (the actual persistence duration is left to the manufacturer and can reach minutes in some cases).
Accordingly, an associate who seeks to conduct an RFID tag-based inventory of a modular of tagged items can be further confused or even mislead when the number of reads is considerably less than what the associate's eyes see. In particular, a given modular of items having an obviously considerable number of tagged items may nevertheless yield only a few current reads when many of the tagged items are presently in the “B” state due to a previous read.
Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present teachings. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present teachings. Certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. The terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.